1. Field of the Invention
The invention relates to enhanced energy absorbing materials and methods of making them. The materials have utility in the manufacture of ballistic vests, hard and soft armor, life protective systems, and anti-ballistic systems.
2. Description of the Prior Art
Materials made from ballistic grade fibers are known in the art, such as the well known aramid fiber-based material sold under the tradename Kevlar®. Methods of processing these materials into finished articles are also known. Ballistic fiber materials, ballistic vest constructions and other materials and methods are described, for example, in U.S. Pat. Nos. 6,276,255; 6,268,301; 6,266,819; 6,248,676; and 6,026,509, which are incorporated by reference. The materials and methods described in these United States Patents may be used, without limitation, in combination with the novel aspects of the invention described herein.
Needle felting, sometimes referred to herein as needle punching or simply needling, is a process used in the textile industry in which an element such as a barbed needle is passed into and out of a fabric to entangle the fibers. Needle felting itself is not new, and is described for example in U.S. Pat. Nos. 5,989,375; 5,388,320; 5,323,523; 3,829,939; and 6,405,417, all of which are incorporated by reference herein.
The use of quasi-unidirectional fabric layers in ballistic materials is known. For example, a quasi-unidirectional fabric is commercially available from Barrday Inc. of Cambridge Ontario, Canada under the trade name Sentinel®. This fabric comprises at least two unidirectional fabric layers cross-laid in a 0/90 configuration relative to each other. These ballistic resistant yarns are woven into a second fabric composed of yarns having substantially lower tenacity and tensile modulus than the ballistic cross-laid yarns to hold the ballistic yarns in place. This method of construction, in theory, forms a fabric substantially stronger than conventional woven materials due to the lack of bending in the ballistic resistant yarns that results from a traditional weaving operation. However, there is a limitation in the performance of such materials due to the inherent lack of stability in the structure. Because the ballistic yarns are not secured in position during a ballistic event, they will spread and allow passage through the interstices by a projectile.
Thus, there continues to be a need for fabrics with high ballistic resistant performance in a dense, compact format which can be conveniently manufactured.